Electro-muscle stimulation (EMS) is well known in the medical art. This technology utilizes a conductive pad or electrode to externally apply a very weak current to a muscle or group of muscles and thereby cause them to contract. The electrode receives an electric stimulation signal from an external voltage/current source, such as an EMS machine. The stimulation signal can be adjusted in amplitude, polarity, frequency, waveform, etc. EMS is commonly used in physical or occupational therapy to strengthen atrophied muscles or paralyzed limbs. It is also used to exercise muscles that are immobilized for long periods of time as a result of muscular or neurological disorders, or extended periods of bed rest arising from injury, surgery, or illness. EMS is also useful for the general exercise of functional muscles to improve muscle tone and strength. For example, athletes can use EMS to treat muscle injuries as a supplement to conventional conditioning exercises. EMS can also be used to recondition muscles or muscle groups which have, for whatever reason, lost their tone and/or strength, have been injured, or are in need of reconditioning to effect cosmetic improvements. An operator who has been trained in the principles of EMS can analyze the areas which are of concern and select the proper muscles to exercise and train.
For example, U.S. Pat. No. 6,341,237 illustrates a device for administrating EMS which includes a flexible covering having a plurality of spaced apart electrodes. In a preferred embodiment, the flexible covering is shaped like a band or belt, and is designed to encircle and be connected around a portion of a patient's body. The band or belt is fabricated from an elastic material so that the electrodes are pressed against the skin of the patient to promote better electrical conduction. Electrodes are selectively positionable to different locations on the flexible covering so they may be placed directly over a selected muscle or muscle group. Each electrode has its individual control for adjusting the level of the electrical stimulation signal so that different muscles can receive different levels of stimulation and the level of stimulation may be changed during the course of treatment. A master adjustment control can be used to adjust the stimulation signal level applied to all electrodes. In a preferred embodiment, the individual adjustment controls are located adjacent their respective electrodes on the flexible covering. U.S. Pat. No. 4,480,830 illustrates a method and apparatus for exercising paralyzed muscles. The method and apparatus make use of a set of transcutaneous electrodes which are placed upon the skin of the subject over muscles which are to be stimulated. A computer controlled stimulator generates a pair of alternately pulsed stimulation signals which are applied across different pairs of stimulation electrodes to produce controlled muscle contraction. Muscle movement is resisted by a dynamic load and a position sensor provides a feedback signal indicating the movement actually achieved. The computer uses the feedback signal for modifying the control signal applied to the stimulator. U.S. Pat. No. 4,499,990 shows a system and method for treating persons with paralyzed legs. The apparatus and method include four sets of transcutaneous electrodes which are placed above the iliac and quadriceps muscles of the paralyzed person. The person is seated upon an exercycle and a series of pulsed stimulation signals are applied to the electrodes to cause coordinated contraction of the iliac and quadriceps muscles. This causes pedaling of the exercycle by the paralyzed legs. A position sensor senses the position of the pedals and transmits an indication thereof to a computer which generates control signals for stimulation driving circuits connected to the stimulation electrodes. U.S. Pat. No. 4,586,495 illustrates an apparatus and method for stimulating muscular activity in an acutely injured patient. A leg which is to be stimulated is strapped into a brace and the leg muscles are stimulated to work isometrically against the brace. The effort exerted by the muscles is measured by load cells which generate feedback signals for a control computer. The computer adjusts the stimulation signals in accordance with the received feedback signals. U.S. Pat. No. 4,586,510 discloses an apparatus for exercising a paralyzed limb by functional electrical stimulation. The system utilizes simple analog devices including a reference signal generator, a position sensor, and an error signal generator. The error signal is integrated to produce a stimulation driving signal for application to the stimulation electrodes mounted on the limb. In the disclosed embodiment, the paralyzed person may be seated in an exercise chair which is equipped with a pair of loading assemblies which are attachable to the legs of the person so as to yieldingly resist the stimulated movement. U.S. Pat. No. 4,724,842 shows a method and apparatus for muscle stimulation. An exercise machine or dynamometer is provided with control apparatus for ascertaining the physical position of a patient during an exercise. The patient is then electrically stimulated over selected ranges of motion in order to aid in the exercise. U.S. Pat. No. 5,070,873 includes a method of and apparatus for electrically stimulating quadriceps muscles of an upper motor unit paraplegic. Muscle fatigue of an electrically stimulated quadriceps muscle of an upper motor neuron paraplegic is detected and compensated for by monitoring the myoelectric (EMG) signal produced by the stimulated muscle and controlling one or more of the following parameters of the electrical stimulation (ES) signal: pulse repetition rate, amplitude, and pulse width. U.S. Pat. No. 5,507,788 illustrates a method and apparatus for controlling skeletal muscle fatigue during electrical stimulation. Electrical stimulation signals are applied to muscles at a frequency which is varied in response to a detected ripple signal in an output tension or torque record which corresponds to the fusion of the multiple muscle contractions. An average torque amplitude is first determined when a stimulation signal is applied at an initial frequency. The amplitude of the ripple on the torque output is then determined and compared to the average torque amplitude to provide a ripple percentage. The measured ripple percentage is compared to a selected ripple percentage corresponding to the desired fusion of the multiple muscle contractions. And the stimulation frequency is adjusted by a feedback loop until the measured ripple percentage conforms to the selected value. U.S. Pat. No. 5,628,722 shows a method for maintaining knee stability of a user suffering from damage to a knee ligament. The method includes a sensor feedback system for measuring abnormal physical relationships between the tibia and femur. The sensor feedback system determines whether selected conditions have been met warranting the application of electrical stimulation and provides information regarding the determination to an electronic stimulator. Electrodes are spaceably mounted on the hamstring and/or quadriceps muscles in electrical communication with the electronic stimulator for causing contraction of the thigh muscles at selected levels, thus providing a posteriorly and/or anteriorly directed force to the upper tibial bone and thereby preventing its instability.